The present invention relates to a pneumatic detector, and in particular, to a pneumatic detector with an integrated alarm and fault switch.
A pneumatic detector is typically comprised of both an alarm switch and a fault switch. Pneumatic detectors typically utilize a pressure tube that contains a gas that will expand as it is heated, thus increasing the pressure in the tube. An alarm switch is used to indicate overheat or fire situations. An alarm switch will include a deformable diaphragm that is at a normal state when the system is at a normal pressure. As the pressure rises, the diaphragm will deform and close an electrical circuit, indicating that there is an alarm condition in the system. A fault switch is used to indicate whether there are leaks, disconnects, or other problems in a pneumatic detector system. A fault switch will include a deformable diaphragm that is deformed when the system is at a normal pressure. If the pressure drops below normal, the diaphragm will resume its normal state and open an electrical circuit, indicating that there is a fault condition in the system.
Pneumatic detectors that utilize both alarm switches and fault switches are used on aircrafts to detect alarm and fault conditions. The pressure tubes for the alarm and fault switches can typically run anywhere from one foot long to fifty feet long, and can be placed in systems that are prone to overheating or fires.